Perhaps you didn't read the article, because its main point is that the official UN forecast is for world population to essentially flatten out at 10.9B around 2100, which is 40% more than today, not 60%.
The important point is that this is a large increase when we already cannot manage now.
Correction: we don't want to manage now. The world has far more than enough wealth and resources to hold climate change to 2 degrees and to stop clear cutting rain forests.
Two thirds of the global extreme poverty (defined by the World Bank as about $1.80/day in current dollars) has been eradicated in just the past two decades.
We're doing awesome.
That’s quite a bit of uncertainty to make any real definitive statements beyond continuing growth expected.
I am mostly simply reacting to people trying to use specific estimates.